A substrate processing apparatus used for substrate processing such as that described above normally comprises a processing unit that includes a plurality of processing chambers where a specific type of processing is executed on substrates, e.g., semiconductor wafers (hereafter may be simply referred to as “wafers”) and a transfer unit connected to the processing unit via, for instance, a load-lock chamber.
The processing unit in a cluster tool-type substrate processing apparatus may be constituted by connecting with a high level of airtightness the plurality of processing chambers and the load-lock chambers around a common transfer chamber normally formed in a rectangular shape. Inside the common transfer chamber, a processing unit-side transfer mechanism constituted with a transfer arm and the like is disposed and wafers are transferred between the plurality of processing chambers and the load-lock chamber by the processing unit-side transfer mechanism. A transfer unit-side transfer mechanism also constituted with a transfer arm and the like is installed at the transfer unit, and wafers are transferred between a cassette container (substrate storage container) containing wafers and the load-lock chamber.
A wafer in a substrate storage container such as a cassette container, which is to undergo the specific type of processing in such a substrate processing apparatus, is first transferred out of the cassette container by the transfer unit-side transfer mechanism at the transfer unit. The unprocessed wafer having been transferred out of the cassette container is then delivered to a positioning device (e.g., an orienter or a pre-alignment stage) disposed in the transfer unit for positioning, before it is transferred into the load-lock chamber. Once the unprocessed wafer is correctly positioned, it is transferred out of the positioning device and delivered into the load-lock chamber.
The unprocessed wafer having been transferred into the load-lock chamber is transferred out of the load-lock chamber by the processing unit-side transfer mechanism, is delivered into a processing chamber where it undergoes the specific type of processing. Once the processing is completed in the processing chamber, the processed wafer is transferred out of the processing chamber by the processing unit-side transfer mechanism and is returned to the load-lock chamber. The processed wafer having been returned to the load-lock chamber is delivered back into the cassette container by the transfer unit-side transfer mechanism.
Even while the processing is in progress in the individual processing chambers, unprocessed wafers are constantly transferred out of the cassette container and are made to wait in standby in the common transfer chamber, the load-lock chamber, the positioning device and the like, since it is desirable to maintain a continuous flow of unprocessed wafers waiting in standby at closest possible positions to the processing chambers to assure the maximum processing throughput from the processing chambers in the substrate processing apparatus. Once the processing on a given wafer is completed in a processing chamber, the processed wafer is immediately taken back into the cassette container and the unprocessed wafers having been waiting in standby are sequentially delivered so as to transfer the unprocessed wafer next in line immediately into the processing chamber.
If an abnormality such as a malfunction, a power supply interruption or an electrical leak occurs while the substrate processing apparatus is in operation, the operation is stopped in an emergency by, for instance, turning off the power to the substrate processing apparatus. Under such circumstances, the wafer processing underway within a processing chamber is halted, and the wafer is left inside the processing chamber. In addition, wafers in a wait state in various chambers such as the transfer unit, the common transfer chamber and the load-lock chamber, too, are also left where they are. If pressure control through, for instance, evacuation has been in progress in a given chamber, the pressure control stops as the operation of the substrate processing apparatus is stopped, which may lead to a reverse flow of dirt and dust from the discharge side and particles of the substances deposited during the wafer processing becoming suspended in the air.
In the related art, if the operation of the substrate processing apparatus stops due to such an abnormality, the abnormality must be corrected before an operator can remove the wafers left in the various chambers of the substrate processing apparatus and manually clean the inside of the chambers, such as the transfer unit, the processing chambers, the common transfer chamber and the load-lock chamber so as to restore the substrate processing apparatus to an operating state.
In the event of an emergency stop of the substrate processing apparatus, the recovery operation for the substrate processing apparatus must be executed manually by the operator as described above in the related art, which is bound to be a laborious and time-consuming process. In addition, since the decision as to exactly what processing needs to be further executed on a wafer having partially undergone the processing in the processing chamber when the processing was halted is made based upon, for instance, a log or the like having stored therein the wafer etching state and the like (see, for instance, Japanese Laid Open Patent Publication No. H11-330185), the wafer salvage processing, too, is bound to be a time-consuming and laborious process, requiring the operator to be both experienced and knowledgeable.
As an alternative, when the power to the substrate processing apparatus is turned on after the operation of the substrate processing apparatus has been stopped due to an abnormality and the abnormality has been subsequently corrected, all the wafers remaining in the transfer unit, the processing chambers, the common transfer chamber, the load-lock chamber are automatically retrieved into the original cassette container by engaging the transfer mechanisms described earlier and the handling of the wafers thus retrieved is entrusted to the operator. However, while the operator does not need to be involved in the wafer retrieval process, he still needs to have significant experience and knowledge in handling the retrieved wafers. Since the decision as to what further processing each wafer needs to undergo cannot be made readily, the wafer retrieval processing is still a time-consuming and laborious process.
Furthermore, if all the wafers left in the substrate processing apparatus at the time of the occurrence of the abnormality are automatically retrieved into the initial cassette container as described above, they are invariably exposed to the outside atmosphere regardless of the specific processing steps the individual wafers were at when the operation of the substrate processing apparatus stopped. However, if a wafer at a certain processing stage, e.g., a wafer undergoing continuous processing at a plurality of processing chambers and currently present in the common transfer chamber to be transferred into the next processing chamber or a wafer undergoing processing in a given processing chamber when the processing is halted, is exposed to the outside atmosphere, the wafer may become unsalvageable. Namely, depending upon the type of processing having been halted, e.g., polysilicon etching, the wafer, once exposed to the outside atmosphere, becomes unfit to undergo the remaining processing (such as additional etching post print and the wafer thus becomes unsalvageable.